1. Field of the Invention
The present arrangement relates to radio frequency transceivers and receivers. More particularly, the present arrangement relates to coding techniques for radio frequency transceivers and receivers.
2. Description of Related Art
Garage Door Opener (GDO) and Remote Keyless Entry (RKE) systems and car alarms utilizing RF (radio frequency) signal have been available for a few decades. In the existing technology two coding schemes of fixed code and rolling code are utilized.
The first generation of such devices utilizes fixed codes which provide a relatively low security against hacking by intruders. In a typical system, both the transmitter and the receiver utilize dip switches with typically 8 to 14 positions. By using standard lab equipment, all the possible combinations of codes and the common frequencies can be produced in a matter of seconds and illegal access to a garage or an automobile or a home can be gained instantaneously.
The second generation of GDO's or RKE systems utilizes rolling code schemes wherein in every transmission anew code which has a mathematical relationship with the previous transmitted codes is transmitted. Devices operating with rolling codes provide comparatively a better protection against unauthorized intrusions than the devices utilizing fixed codes but they are also prone to unauthorized intrusions. An individual who has a temporary access to the GDO or RKE remotes, e.g., a parking attendant cannot utilize the copied code from a rolling code device to activate a garage door or unlock a car door. However, if the code is captured, the mathematical relationship which governs the code generation eventually can determined and illegal access to a garage or an automobile can be gained, as there are already aftermarket transmitters sold which utilize rolling codes.
Furthermore, by utilizing simple equipment, hackers can gain illegal access to a garage or a car in a matter of hours as opposed to minutes due to fact that the rolling codes typically contain longer sequence of bits.
As explained bellow, both types of systems, i.e., fixed and rolling codes are vulnerable to security issues and their installation and use require significant inconveniences.
Vulnerabilities & Disadvantages of Fixed Code Systems
(1) RF Generator and Counter can be Used for Unauthorized Intrusion.
An intruder can utilize a simple setup, i.e., an RF (Radio Frequency) signal generator which has pulse amplitude modulation capability in conjunction with a binary counter circuit and an antenna in order to illegally break into a garage or a vehicle. The signal generator is consecutively tuned to each of the known frequencies at a time whilst the binary counter circuit produces all the possible binary combination modulating the RF signal from the RE generator feeding the antenna. Using such an arrangement for a typical fixed code system utilizing 14 bits in a period of less than a minute any garage door can be opened or an automobile lock can be deactivated. I.e., in a 14 bit fixed code scheme, there is a combination of 214=4096 possible codes. For a burst length of 1 mS (millisecond) which typically is required for activating a GDO, RKE or RFHE a period of 1 mS×4096=4.1 seconds is the required time for each of the commonly used frequencies. In order to go through the 10 different common frequencies for producing the 4096 different combinations of codes with the binary counter circuit only, it takes only a time period of about 41 seconds for opening a garage door or an automobile door.
(2) A Glance at the Dip Switch is Sufficient to Obtain the Code.
An intruder who has a temporary access to a GDO/RKE/RFHE transmitter unit, e.g., a parking attendant, can look at the dip switch combination and copies the code of the GDO/RKE/RFHE transmitter unit.
(3) Use of Universal/Trainable Garage Door Opener to Copy the Code.
An intruder who has a temporary access to a GDO/RKE/RFHE transmitter unit, e.g., a parking attendant, can utilize a universal (Trainable) Garage Door Opener to copy the code and frequency of the GDO/RKE/RFHE.
(4) Accessibility to the Premises Even after Expiration of the Subscription.
In parking lots of apartment building complexes or office buildings, often the tenants/parking subscribers are changed. However, after tenants leave the complex or their subscriptions to the parking expire, they could still use their fixed code/rolling code transmitters and illegitimately access the premises.
(5) Code Grabbing.
An intruder who is staying nearby the site can utilize receivers or spectrum analyzers to determine the frequency and the code.
(6) Universal Garage Door Opener Incompatibilities.
Very often a universal garage door opener cannot learn the frequency or code of an existing garage door opener. For instance, due to the very short transmission time of the code and the super heterodyne receiver in the universal garage door openers are not at the appropriate frequency window when the transmitter is transmitting. E.g., in the Canadian garage door openers, only 1-2 seconds of transmission is allowed and the user has to keep pushing the transmitter button repeatedly so that eventually the universal Garage Door Opener detects the frequency and the code. Nonetheless, in such cases, special skills are required, i.e., if the speed of pushing the transmitter button is too fast or too slow, the UGDO does not get trained.
(7) Nuisances and Inconveniences with the Add-on Receivers.
Often, when the universal garage door opener is incompatible, the user has to utilize an add-on receiver. The addition of such receiver either requires climbing a ladder and wiring or wiring to the door switch which poses safety risks of falls, electrocution or other accidents/hazards and expense and delays of hiring a professional for installation which is nuisance and significant inconvenience to the users. As the various models of door switches operate at different voltages, e.g., 28 V DC, 110 AC, 220 AC, the sellers of add-on receivers are hesitant to provide their units to average users who are lack the sufficient knowledge and experience and potentially could be subject to risks of falls and/or electrocution.
Vulnerabilities & Disadvantages of Rolling Code Systems
(1) RF Generator and Counter can Break Rolling Codes.
Similar to the fixed code case as discussed above, in a rolling code system, an intruder using an RF signal generator and a binary counter circuit would still be able to produce the appropriate code and frequency after some time and illegally access entry into a garage or unlock a car door.
(2) Rolling Codes are Subject to Hacking.
Typically rolling codes are created by utilizing a digital feedback control system. Both types LFSR (Linear Feedback Shift Register) and NLFSR (Non-Linear Feedback Shift Register) are commonly used in cryptography algorithms such as those generated in rolling code systems. Systems utilizing NLFSR are known to be more resistant to cryptanalytic hacking than systems utilizing LFSR, i.e., NLFSR systems are breakable after longer periods than LFSR systems. The aftermarket transmitters which utilize rolling codes have already become available to the consumers and are currently being sold confirming that the rolling code systems are not quite as secure as it used to be perceived.
(3) One Time Access to the Garage is Sufficient to Gain Permanent Access.
In a rolling code system, a person who has a temporary access to the entrance area of the garage, e.g., a worker can easily program the receiver with his/her rolling code transmitter and illegally access the premises at later times.
(4) Difficulties Associated with Adding a New Transmitter with Roiling Codes.
Often the users would need to purchase more GDO transmitters (e.g., as a result of damage, loss or purchase of new vehicles). New transmitters are either ordered from the original equipment manufacturer or an aftermarket manufacturer or alternatively utilize universal transmitters capable of handling rolling codes which are available in some automobiles. In order to add any of such transmitters, often in order to provide the “cryptographic key” to the receiver, the receiver needs to be trained which necessitates accessing and pressing the training button located on the receiver unit while the transmitter is transmitting a signal. The receiver units are commonly mounted adjacent to the garage door opener motors which are installed at 7-10 ft above the garage floor. Accessing the receiver is required for every new transmitter/universal transmitter purchase and requires climbing a ladder by some one with sufficient technical background.
(5) Accessibility to the Premises Even after Expiration of the Subscription.
Similar to the fixed codes, in parking lots of apartment building complexes or office buildings, regularly the tenants/parking subscribers leave and are replaced with new tenants/parking subscribers. However, after tenants formally leave the complex or their subscription to the parking expires, they could still use their fixed code/rolling code transmitters and illegitimately access the premises.
(6) Code Grabbing.
An intruder who stays nearby the site can utilize receivers to determine the frequency and the code and use the hacked coding scheme to generate the subsequent codes as there are already aftermarket transmitters sold which utilize rolling codes.
(7) Universal Garage Door Opener Incompatibilities.
Often the universal garage door openers cannot be trained to produce the frequency or the rolling codes which necessitates changing the receiver or utilizing an additional receiver.
(9) Nuisances and Inconveniences with the Add-on Receivers.
Often, when the universal garage door opener is incompatible, the users utilize add-on receiver which necessitates either climbing ladders which pose safety issues such as risks of falls, electrocution or installing wires to the door switch. Both methods entail expenses and delays of hiring a professional for installation which are nuisance and inconvenience to the users.
Whereby, a superior system which the present invention embodies which can provide a higher security with more user-friendly methodology of activating and dc-activating new transmitters is necessary.